The Smilax species are weedy vines native to North America. These vines are difficult to control that can interweave through ornamental landscape shrubs.
There are ten common Smilax species in South Carolina, along with five less common species. Many common names include catbriers, greenbriers, hogbriers, bullbriers, prickly-ivies, deer thorns, and smilaxes. They are evergreen to partially deciduous plants, produce strong tendrils to aid in support, and have thorns along the vines. Greenbriers are perennial vines that can grow in the understory with low light conditions, that allows for rapid growth beneath shrubs to become well established.
Greenbrier vines are dioecious, meaning there are separate female and male plants. Female plants produce clusters of small 1/4-1/2 inch blue-black, black, or red fruits. Small mammals and birds eat these fruits in the winter and spread the seeds.
Greenbriers have extensive, knobby rhizomes that are extremely difficult to pull out of the ground. Each rhizome can sprout additional fast-growing vines from a few inches to several feet from the original vine. These rhizomes can quickly regenerate new vines after being cut, damaged by fire, or treated with weed killers.
Larger vines can grow upright at least six feet. The tendrils allow the vines to stabilize their height by hanging onto shrub branches and tree limbs. The tendrils start out as green and pliable, but once wrapped around a branch, they mature and harden. Thickets can be formed by sprawling out and between nearby shrubs and trees. Greenbriers can grow as high as 30 feet when using woody plants for support. Thorns of greenbriers can be green and small on some species, while others are multi-colored. The thorns aid in support of the vine to snag on nearby branches.
Chemical control of greenbriers is difficult because of their waxy foliage and root system. If there are only a few small plants, it is possible to dig up the rhizomes. If it is a larger vine, chemical treatments will be necessary. Most chemical sprays will not penetrate the waxy coating on mature foliage. Therefore, cut the vine and spray after they resprout tender new growth. Wait until the regrowth is 1/2 to 1 foot tall and spray with a 10% solution of glyphosate. To make a one-gallon solution in a pump-up sprayer, add 13 fluid ounces of 41% concentrate glyphosate product and top off with water. One can always wait until early spring to spray new growth. If the vines are near desirable shrubbery, cut the vines near the soil line and pull out the vine. Spray or paint the freshly cut vine stump with a 10% glyphosate solution. Glyphosate has very little soil activity and should be absorbed by the roots of landscape plants nearby.
Triclopyr is an herbicide that is absorbed by mature foliage on greenbriers. Spray the foliage with a triclopyr solution of either 9 fluid ounces of 61.6% product with water to make a gallon of spray or a 50:50 mix of 8 or 8.8% product with equal amount of water. Triclopyr solutions can also be sprayed or brushed on freshly cut stumps. There is some soil activity with triclopyr, so do not use near desirable landscape plants.
For more information on smilax or examples of brands and specific products used to control greenbriers, please visit the Home and Garden Information Center website at hgic.clemson.edu. Tune in on Tuesday nights to watch “Making it Grow” at 7 p.m. on SCETV or mig.org. Email Outen at callenb@clemson.edu.
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